Development of electric melting furnace
In 1902, Voelker was granted a basic patent for the use of heat generated by passing an electric current through a glass batch to melt glass. It was discovered that glass is an electrical conductor at high temperatures. The alkali metal sodium and potassium ions contained in the molten glass have electrical conductivity. When current passes through, Joule heat will be generated. If the heat is large enough, it can be used to melt the glass. That is, an electric melting furnace is used to melt glass. With the continuous improvement and development of furnace design and electrodes, this electrofusion method has become widely used. Then a company in Norway achieved full electrofusion of glass using graphite electrodes. Swedish companies use this electric furnace to produce amber and green glass. The electric melting furnace adopts thin layer feeding method, and the batch materials float on the surface of the glass liquid. When the electric melting furnace is put into operation, it is equipped with a temporary furnace cover. When the glass liquid level covers the electrode, the furnace cover is removed. The electrodes used are large iron blocks. Since the iron electrodes color the glass, this furnace can only be used to melt colored glass. The effect is quite good. It can reach 1.40kWh/kg glass at that time, but this method is more suitable for electric energy prices. low areas.
Glass tank kilns that use flame surface heating have a long history. Although many structural improvements have been made during long-term use, they still have some serious shortcomings such as low thermal efficiency, complex kiln structure, large volume, and harsh working environment. The all-electric melting furnace has outstanding advantages in terms of use effects, which are as follows: simple furnace structure, small footprint, stable control and easy operation, and reducing the scattering and volatilization of some expensive oxides in the raw materials, low noise, and Reduced environmental impact, stable melting process and improved product quality are all unmatched by fuel furnaces.
The main principle of an electric melting furnace is to use electricity as the heat source. Generally, silicon carbide or molybdenum disilicide resistance heating elements are installed on the side walls of the kiln, the bottom oblique insert, the furnace top and other locations to perform indirect resistance radiation heating. Some crucible kilns for melting special glass use induction heating, which relies on the induction of eddy currents in the kiln and the glass liquid for heating. The pool kiln directly uses the molten glass in the kiln as a heating resistor. Multiple groups and layers of electrodes can be arranged at different depths of the molten glass to heat the molten glass, and the temperature system can be controlled by adjusting the power consumption. When this method is used, the temperature of the space above the glass liquid level is very low (called cold furnace top), so the energy is basically consumed in melting the glass and dissipating heat from the kiln wall. There is no loss of heat taken away by the flue gas and no impact on the environment when the flue gas is discharged. pollution, high heat utilization, and no need to set up a combustion system and waste heat recovery system. The all-battery kiln can be automatically controlled, requires fewer management personnel, and has good working conditions. The disadvantage is that it consumes large power resources. Suitable for melting refractory glass, volatile glass and dark-colored glass. The large-scale battery kiln's production capacity of bottle glass reaches 150t per day.
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